DESCRIPTION: The focus of this proposal is on spatial and attentional features of auditory perception in complex auditory environments. The methods use those of psychophysics and cognitive psychology, with a primary goal being to provide objective realism in the stimuli and listening environment while maintaining the empirical control necessary to quantify perception. To this end, much of the work will be done in a simulated open field listening environment (SOFE) that allows presentation of multiple sources and echoes from arbitrarily chosen locations along with related visual stimuli. The hope is to move closer to an understanding of the perception of multiple sources (as occurs in the so-called cocktail party effect) in the presence of reverberation. The SOFE will also be used study other auditory aspects of hearing such as binaural adaptation, motion, distance perception and the spatial features of visual/auditory fusion. In parallel with basic psychophysics will be studies of auditory attention and its role in stimulus selection. Special interest will be focussed on results showing that detections based on comparisons to sensory traces place no demands on divided attention while comparisons to absolute standards in long term memory do. Related studies of cued attention will be applied to higher-order auditory information that is derived at levels of processing central to the auditory filters. More specially, these include localization, musical pitch, timbre and the temporal relations of stimuli. This work has direct importance for current development of programmable hearing aids and cochlear prostheses, especially because of the need to understand the processing of complex stimuli in reverberant space and the role of shared attention.